The load-bearing properties of spectrophotometer cuvettes
Nigel C. Eastmond
Division of Biochemical Science, Rowett Research Institute, Aberdeen.
Now: Dept. Pharmacology and Therapeutics, University of Liverpool, Liverpool.
Address for correspondence:
Dept. Pharmacology and Therapeutics, University of Liverpool, Liverpool.
Introduction
Spectrophotometer cuvettes are common laboratory items used in the measurement
of the light and U.V. absorbative properties of liquids. Most cuvettes are
designed to have a path length of 1 cm and hold approximately 4 ml of fluid.
The cuvettes are made from a variety of material. Quartz cuvettes are reusable,
expensive and used mainly for accurate work such as nucleic acid quantitaion.
Disposable plastic cuvettes are very cheap and are used for less demanding
assays such as Lowry or Bradford protein assays.
Previous studies have shown that cuvettes are well suited to the application
of spectrophotometry, but as yet, no further uses have been found for them.
It is noted that the plastic cuvette is a very accurately manufactured item
having a path length of 1 cm throughout it's length. It is known that in the
manufacture of compression loading structures such as bridges, parallel-sided
tubes, if accurately made, are very strong when loaded vertically. It is
suggested that spectrophotometer cuvettes may share this property.
This study aims to establish whether plastic disposable spectrophotometer
cuvettes have strucural properties way beyond their original design.
Materials and Methods
A spectrophotometer cuvette (Sarstedt) was placed vertically, in it's normal
orientation on the linoleum floor of a laboratory. Wearing a pair of heavy
brown brouges (Churches Shoes, London), a human experimental subject
(11.5 stone) was balanced with one foot, on the top of the cuvette.
Throughout the procedure, the cuvette was observed for signs of cracking.
Fresh cuvettes were used in subsequent experiments on heavier subjects as
they happened to be passing the lab.
Results
In all the experiments performed, the spectrophotometer cuvettes never broke.
Subjects of up to 16 stone in weight were used with 100 % success. However,
it is noted that no cuvettes survived similar experiments when placed on their
side.
Discussion
It is clear from the present study that spectrophotometer cuvettes, placed
vertically are extraordinarily strong. This study did not find the limits of
this durability but we do not doubt that considerably more load could be
applied with equal success. Indeed, collaborative workes have done preliminary
experiments where a 12 channel Grass Polygraph machine has been used to load
the cuvettes. The results of these experiments also seem promising (personal
communication).
The present study also investigated the appliction of lateral compression on
the cuvettes and found them not to be strong. Again, the limits of this
structural property were not found.
The authors postulate that different cuvettes may have different load-bearing
properties. It is noted that certain cuvettes are supplied with attractive
flutings and it is possible that such embellishments may endow the humble
disposable with more strength than standard plain-faced cuvettes. Furthermore,
while expensive, quartz cuvettes may have even more strength than that.
It is even possible that four such cuvettes could support the weight of
a carefully balanced Volvo.
This work was submitted in shorter form to bionet.molbio.methds_reagnts in
1995.
Dr. Nigel C. Eastmond | Email nce at liv.ac.uk
Dept. Pharmacology and Therapeutics | Tel. +44 (0)151 794 5541
University of Liverpool | Fax. +44 (0)151 794 5540
Liverpool L69 3BX |